Rare-gas-discharge lamp

ABSTRACT

A rare-gas-discharge lamp, wherein the electrodes pass, at least over a portion of their length, within refractory and dielectric screens having at least an opening which allows the discharge propagation and has linear size much smaller than the screened length of each electrode so that, when the discharge occurs, a nearly punctate light source is obtained.

United States Patent 1 [111 3,898,502 Garrone Aug. 5, 1975 RARE-GAS-DISCHARGE LAMP [76] inventor: Giulio Garrone, Strada Comunale PmYMry ,Rolmec Mirafiori 35b7, Turin Italy Assistant E.\'ammerDarw1n R. Hostetter [22] Filed: July 11, 1974 [21] Appl. No.: 487,561

[57] ABSTRACT [30] Foreign Application Priority Data July 17 1973 Italy l l 69131/73 A rare-gas-discharge lamp, wherein the electrodes v v v pass, at least over a portion of their length, within re- [52] U5. CL 313/205. 313/224. 313/212. fractory and dielectric screens having at least an open- 313/213 ing which allows the discharge propagation and has [51] Int Cl H01 j 61/10 linear size much smaller than the screened length of 58 Field of 's' a..1111I11I'.Z11I'.11'.111111111111I1..... 313/205 each electmde that when the discharge Occurs, a

. nearly punctate light source is obtained.

[56] References Cited UNITED STATES PATENTS 5 Claims, 1 Drawing Figure 3.829.733 8/1974 Belyaeu et al. 313/205 RARE-GAS-DISCHARGE LAMP The present invention relates to a rare-gasdischarge lamp, which may operate at very short impulses and at very high frequency, and in which the discharge occurs along a path which is short and concentrated in a restricted space, so as to create a substantially punctate light source.

The lamp according to the invention comprises a glass bulb filled with a rare-gas, particularly xenon, at the interior of which a pair of electrodes extend, and is characterized in that the said electrodes, at least over a portion of their length, pass within screens formed by small tubes of a refractory and electrically insulating material, which tubes have at least one opening which allows the discharge to propagate from one electrode to the other one, and has linear size much smaller than the length of the portion of each electrode which is screened by the said tubes.

Due to the presence of these screens and to the reduced size of the openings, the discharge starts from a restricted area thereby creating a practically punctate source, and is confined in a reduced space where a greater pressure of gas is obtained, so that a ionization glow is obtained which is more intense that that of the lamps of known type.

Advantageously the said tubes have a single opening realized in correspondence with the end portion of each electrode. It is not excluded however the presence of at least an opening, also practically punctate, realized for instance on the side surface of each said tube, in alternative or in addition to the opening realized in correspondence of the end portion of the electrodes.

In any casein correspondence of the said opening (s) the electrodes will be provided, in a known manner, with a covering of a material having a good power of thermionic emission, so as to assist in the priming of the discharge.

Further characteristics of the invention will result from the following description, with reference to the accompanying drawing, which diagrammatically shows a cross sectional view of a preferred embodiment of a lamp according to the invention.

As shown in the drawing, a rare-gas-discharge lamp according to the invention comprises a glass bulb 1, filled preferably with xenon, at the interior of which a pair of electrodes 2, 3 extend.

In order to limit the extent of the region in which the discharge occurs, the electrodes 2, 3, at least in their end portion pass within dielectric and refractory screens formed by small tubes 8 and respectively 9, preferably made of quartz, and open for instance in correspondence of the extremities 4, of the electrodes 2, 3.

In this way the discharge takes place only between the said extremities 4, 5 and forms a practically punctate light source. The discharge path is shown by the arrows 10 in the drawing.

In correspondence of the extremities 4, 5 the electrodes 2, 3 are also provided with a covering of a material, known in se having a good thermionic emissive power. The presence of this covering facilitates the priming of the discharge 10.

The drawing still shows that the tubes 8, 9 are retained on the respective electrodes by respective springs 6, 7 coaxially arranged around the electrodes within the said tubes, to the inner surface of which the springs adhere over at least a portion of their length. Advantageously said springs are made of molybdenum.

The presence of the tubes 8, 9, which makes practically punctate the portion of each electrode serving as starting zone for the discharge 10, results in the discharge being confmed in a greatly reduced part of the inner space of the bulb 1, so that a brilliancy more concentrated than that provided by the discharge lamps at present in use is obtained. I

This feature, together with the possibility of operating at impulses, makes the lamp of the invention particularly suitable for cinematographic uses and for all other applications in which a dimensionally reduced discharge is necessary or useful.

It is self evident that the above description is given only by way of a non limitative example, changes and modifications being possible without departing from the scope of the invention.

Thus, for instance, the screening tubes 8, 9 could have an opening in their facing side surfaces, instead of the opening realized in correspondence of the end portions 4, 5 of the electrodes (which in this case would be shaped as small cylinders closed at one base and open on the side), or, if it is desired, the said side opening could be provided in addition to the other opening.

In any case, also the size of that side opening will be very small, that is such as to give rise to a practically punctate light source. Also in correspondence of this side opening a covering of a material with a good thermionic emissive power will be provided.

Lastly it is possible to form the electrodes from a metal or a metal alloy with high thermionic emission, such as thorium, beryllium and the like, so that the said covering becomes superfluous.

What I claim is:

l. A rare-gas-discharge lamp, comprising a glass bulb filled with a rare gas into which bulb the electrodes penetrate, characterized in that each electrode passes, at least over a portion of its length, within a refractory and dielectric screen provided with at least an opening allowing the discharge propagation and having linear size much smaller than the length of the electrode portion which is screened, so that, when the discharge occurs, a nearly punctate light source is obtained.

2. A lamp according to claim 1, characterized in that the said screens are formed by small tubes of quartz which cover the end portion of each electrode.

3. A lamp according to claim 1, characterized in that the said tubes have a single opening preferably realized in correspondence of the free end of the electrodes.

4. A lamp according to claim 1 characterized in that the said electrodes are formed by a mass of a metal or of a metal alloy having a good thermionic emissive power.

5. A lamp according to claim 2, characterized in that the said tubes are retained on the respective electrodes by springs of molybdenum, which springs are arranged within said tubes and around the electrodes and are in contact with the inner surface of the said tubes at least over a portion of their length. 

1. A rare-gas-discharge lamp, comprising a glass bulb filled with a rare gas into which bulb the electrodes penetrate, characterized in that each electrode passes, at least over a portion of its length, within a refractory and dielectric screen provided with at least an opening allowing the discharge propagation and having linear size much smaller than the length of the electrode portion which is screened, so that, when the discharge occurs, a nearly punctate light source is obtained.
 2. A lamp according to claim 1, characterized in that the said screens are formed by small tubes of quartz which cover the end portion of each electrode.
 3. A lamp according to claim 1, characterized in that the said tubes have a single opening preferably realized in correspondence of the free end of the electrodes.
 4. A lamp according to claim 1 characterized in that the said electrodes are formed by a mass of a metal or of a metal alloy having a good thermionic emissive power.
 5. A lamp according to claim 2, characterized in that the said tubes are retained on the respective electrodes by springs of molybdenum, which springs are arranged within said tubes and around the electrodes and are in contact with the inner surface of the said tubes at least over a portion of their length. 